CC2500-RTR1 datasheet(36/84 Pages) TI

36 / 84 page

CC2500

PRELIMINARY Data Sheet (Rev.1.2)

SWRS040A

Page 36 of 83

CC2500 has a built-in state machine that is

used to switch between different operation

states (modes). The change of state is done

either by using command strobes or by

internal events such as TX FIFO underflow.

A simplified state diagram, together with

typical usage and current consumption, is

shown in Figure 5 on page 13. The complete

radio control state diagram is shown in Figure

15. The numbers refer to the state number

readable in the MARCSTATE status register.

This register is primarily for test purposes.

19.1

Power-On Start-Up Sequence

When the power supply is turned on, the

system must be reset. One of the following two

sequences must be followed: Automatic

power-on reset (POR) or manual reset.

19.1.1 Automatic POR

A power-on reset circuit is included in the

CC2500. The minimum requirements stated in

Section 4.9 must be followed for the power-on

reset to function properly. The internal power-

up sequence is completed when CHIP_RDYn

goes low. CHIP_RDYn is observed on the SO

pin after CSn is pulled low. See Section 10.1

for more details on CHIP_RDYn.

When the

CC2500 reset is completed the chip

will be in the IDLE state and the crystal

oscillator running. If the chip has had sufficient

time for the crystal oscillator and voltage

regulator to stabilize after the power-on-reset,

the SO pin will go low immediately after taking

CSn

low. If CSn is taken low before reset is

completed the SO pin will first go high,

indicating that the crystal oscillator and voltage

regulator is not stabilized, before going low as

shown in Figure 16.

CSn

XOSC and voltage

regulator stabilized

Figure 16: Power-on reset

19.1.2 Manual Reset

The other global reset possibility on

CC2500 is

the SRES command strobe. By issuing this

strobe, all internal registers and states are set

to the default, IDLE state. The manual power-

up sequence is as follows (see Figure 17):

•

Set SCLK=1 and SI=0, to avoid potential

problems with pin control mode (see

Section 11.3 on page 23).

•

Strobe CSn low / high.

•

Hold CSn high for at least 40 µs relative to

pulling CSn low

•

Pull CSn low and wait for SO to go low

(CHIP_RDYn).

•

Issue the SRES strobe on the SI line.

•

When SO goes low again, reset is

complete and the chip is in the IDLE state.

CSn

XOSC and voltage

regulator stabilized

XOSC and voltage regulator switched on

SRES

40 us

Figure 17: Power-on reset with SRES

Note that the above reset procedure is only

required just after the power supply is first

turned on. If the user wants to reset the

CC2500 after this, it is only necessary to issue

an SRES command strobe.

19.2

Crystal Control

The crystal oscillator (XOSC) is either

automatically controlled or always on, if

MCSM0.XOSC_FORCE_ON

is set.

In the automatic mode, the XOSC will be

turned off if the SXOFF or SPWD command

strobes are issued; the state machine then

goes to XOFF or SLEEP respectively. This

can only be done from the IDLE state. The

XOSC will be turned off when CSn is released

(goes high). The XOSC will be automatically

turned on again when CSn goes low. The state

machine will then go to the IDLE state. The SO

pin on the SPI interface must be zero before

the SPI interface is ready to be used; as

described in Section 10.1 on page 21.

CC2500-RTR1 数据表(PDF) 36 Page - Texas Instruments

CC2500-RTR1 数据表(HTML) 36 Page - Texas Instruments

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